Adjust pH to 5.6 with 20% lactic acid or HCl. Fresh yeast extract is
prepared by autoclaving a 20% suspension of commercial baker´s yeast in
distilled water for 30 min at 121°C, allowing the suspension to settle
overnight at 2 to 8°C, decanting and further clarifying the supernatant by
centrifugation. The extract prepared in this manner contains 1.5% solids
and if not to be used within a few days, should be frozen or freeze-dried
immediately.
